The semiconductor transistor typified by TFT shows the current trend towards spreading of its applications along with the development of display devices. Such a semiconductor transistor functions as a switching element when the electrodes are connected through a semiconductor material.
Here, as shown in FIGS. 13A and 13B, a transistor 100 using the semiconductor material normally comprises: a gate electrode 101, a gate insulation layer 102 for insulating the gate electrode 101, a semiconductor layer 103 made of the semiconductor material, a source electrode 104 and a drain electrode 105 formed so as to contact to the semiconductor layer 103. As such transistor, a transistor having a bottom-gate structure where the gate electrode 101 is provided to the under surface side of the semiconductor layer 103 (FIG. 13A) and a transistor having a top-gate structure where the gate electrode 101 is provided to the upper surface side of the semiconductor layer 103 (FIG. 13B) are known.
As the semiconductor material used for the semiconductor transistor, inorganic semiconductor materials such as silicon (Si), gallium arsenic (GaAs) and indium gallium arsenic (InGaAs) are conventionally used. Semiconductor transistors using such an inorganic semiconductor are also used for display TFT array substrates of liquid crystal display devices which have been widely spread in recent years. On the other hand, organic semiconductor materials made of organic compounds are known as the semiconductor material.
Transistors using such organic semiconductor materials have an advantage in that: they are allowed to be increased in area at a lower cost than those using the inorganic semiconductor materials, and they can be formed on a flexible plastic substrate and are also stable against mechanical impact. Therefore, active studies are being made as to technologies regarding the organic semiconductor materials, which is assumed to be applied display devices, such as flexible displays typified by electronic papers, in the next generation. In particular, focuses on studies of a manufacturing method which improves the transistor performance and allows high productivity are made.
In these circumstances, Patent Literature 1 discloses a method of forming an organic transistor by using a liquid crystalline organic semiconductor material as an organic semiconductor material which constitutes an organic semiconductor layer and coating a coating solution containing the organic semiconductor material. As such method allows the liquid crystalline organic semiconductor material to align in the organic semiconductor layer, it has an advantage in improving a performance of the organic transistor to be manufactured. In manufacturing a high-performance organic semiconductor device having high industrial versatility, organic transistor to be manufactured is desired to have a technical structure where plural organic transistors are provided on a substrate. However, the method of Patent Literature 1 has a problem that it is very difficult for the method to manufacture an organic semiconductor device which has such technical structure because it is difficult to form plural organic semiconductor layers in pattern.
To respond such problem, Patent Literature 2 discloses a method of forming an organic transistor by using a laminate, which has a technical structure where an organic semiconductor layer containing a liquid crystalline organic semiconductor material aligned regularly on a substrate provided with an alignment film, and by transferring the organic semiconductor layer from the laminate. According to this method, by transferring the organic semiconductor layers in pattern, it is possible to manufacture an organic semiconductor device which has a technical structure where plural organic transistors are provided on a substrate. However, it is still difficult to transfer an organic semiconductor layers in highly-precise pattern in such method. Further, to begin with, when an organic transistor is manufactured by such a method, there is a problem of lowering a performance of the organic transistor to be manufactured because alignment of the liquid crystalline organic semiconductor material in the organic semiconductor layer is deteriorated due to the heating of or pressing to the organic semiconductor layer at the time of transferring the organic semiconductor layer. Although possibility of avoiding such problem remains by transferring the organic semiconductor layer under milder conditions, such conditions will largely limit the transferring conditions, and thereby resulting in raising another problem of making it impossible to manufacture an organic transistor with high productivity.
Patent Literature 1: Japanese Patent Application Laid-open (JP-A) No. 2006-339473
Patent Literature 2: JP-A No. 2007-96288